Israel will strike back "fiercely" if Syria attacks the Jewish state, Prime Minister Benjamin Netanyahu said Tuesday, as the US mulled military action against President Bashar al-Assad's regime.

"The State of Israel is prepared for every scenario," he said following consultations on the crisis in Syria. "We are not part of the civil war in Syria, but if we detect any attempt to hurt us, we will react, and react fiercely."

Netanyahu's remarks came as Syria vowed to defend itself if the United States and its allies attacked the Assad regime, which allegedly used chemical weapons against its own citizens last week.

Syrian Foreign Minister Walid Muallem said their capabilities would "surprise" the world, and warned that any military action against it would serve the interests of Israel and Al-Qaeda.

Washington has accused Assad's regime of a cover-up, and has said it will provide more evidence of who was behind the attacks. US Defence Secretary Chuck Hagel said the military was prepared to act if Obama called for it.

Meanwhile, Israelis were rushing to replace old gas masks. A spokeswoman for the Israel Postal Service, which distributes the masks, said there has been a 300 percent increase in delivery orders in recent days.

Intelligence Minister Yuval Steinitz on Monday called the notion of Assad attacking Israel "insane".